1. Field of the Invention
The present invention relates generally to field of automated controls. More specifically, the present invention is directed to a regulator for heating and air-conditioning appliances in motor vehicles. The device employs a suction fan which is driven by an electrically commutated DC motor and a temperature measurement sensor arranged in the induction air flow.
2. Description of the Related Art
Regulators for heating and air-conditioning appliances are used to determine the interior temperature in motor vehicles. In these devices, an electrically powered suction fan is used to suck air out of the interior of the vehicle and to move it past a temperature measurement sensor. The temperature measured by the temperature measurement sensor is used to regulate the heating and air-conditioning appliance. Since only a small amount of air is sucked out of the passenger compartment, low-power electrically commutated DC motors are used to drive the suction fan, and also have the advantage that they produce little noise.
In order to ensure that the electrically commutated DC motor starts reliably, it is known for appropriate motors to be used whose starting is ensured by means of an integrated Hall sensor. However, Hall sensors are relatively expensive components. German Patent Application DE 43 40 580 furthermore discloses a regulator for heating and air-conditioning appliances, in which there is no Hall sensor.
In order, nevertheless, to ensure that the electrically commutated DC motor starts reliably, this invention proposes that an interrupter be arranged in the circuit of the DC motor. The interrupter is actuated by a timer and is used to interrupt the motor supply voltage cyclically, in a pulsed manner. As a result of this measure, when the supply voltage is built up once again in the starting phase, the motor receives rotation impulses at regular time intervals, which ensure starting by virtue of their continual repetition.
The mass inertia of the rotating fan bridges the current interruption, which lasts for only fractions of a second, so that there is no reduction in the measured air flow sufficient to adversely affect the measurement results in any way, and the motor is not overloaded. However, if the motor fails to start despite these measures, or if the motor remains stationary during operation for any reason whatsoever, then this results in no air being conveyed out of the interior of the vehicle or past the temperature measurement sensor. Consequently, the air-conditioning regulating process is based on an incorrect actual value of the internal temperature.